The electric field at a point between two point charges, on the line joining them, is zero. What can you say about the charges?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → They have the same sign.
The field of a positive charge points away from it, and the field of a negative charge points towards it. At a point between two charges, the two fields can cancel only if they point in opposite directions.
Option (1) They have opposite signs. — Incorrect. Between a positive and a negative charge, both fields point towards the negative charge. They add, so the field cannot be zero there.
Option (2) They have the same magnitude. — Incorrect. Equal magnitudes are not needed. For two unequal like charges, the zero-field point still lies between them, nearer the smaller charge.
Option (3) They have the same sign. — Correct. Between two like charges, the two fields point in opposite directions. At one point their sizes are equal, and the net field is zero.
Option (4) They have different magnitudes. — Incorrect. Different magnitudes are not needed either. Two equal like charges give zero field at the midpoint.
NCERT (2026-27):
Electric Field Lines – “… The field lines of a single positive charge are radially outward while those of a single negative charge are radially inward. …”